Partitioning key
A partitioning key is a value or attribute used to determine which partition stores or receives a record or data item.
ScyllaDB in Action
A partition key is the key component that determines a row’s partition and enables routing a query to the node owning that partition.
- How it is used
- Guides query-first table design so requests route to the partitions needed for application reads and writes.
- How deep it goes
- Defines partitioning keys, traces hashing and node routing, and develops selection trade-offs including denormalization and bucketing.
- Examples
- Uses restaurant food reviews and author-, date-, and score-partitioned article-summary tables.
- What you can do after
- Design tables around named access patterns and query efficiently by supplying the partitioning key.
Kafka for Architects
A message key is a Kafka record value used to determine partition placement and associate records for ordering.
- How it is used
- Uses message keys to place related events in one partition when their processing order matters.
- How deep it goes
- Explains default key-based selection, null-key behavior, alternatives, and design trade-offs without a low-level implementation walkthrough.
- Examples
- Uses account balances, customer address updates, transaction IDs, and an AsyncAPI customer-profile binding.
- What you can do after
- Evaluate/understand which message key preserves required ordering while supporting suitable partition load distribution.
Apache Kafka in Action
A message key is an optional Kafka message attribute used to categorize a message and determine its partition.
- How it is used
- Groups related price updates in one partition so their production order can be preserved.
- How deep it goes
- Explains optional message keys, console commands, hash-modulo partitioning, and operational pitfalls without deriving the hash algorithm.
- Examples
- Uses keyed product-price updates, console producer and consumer commands, and a Python producer call.
- What you can do after
- Operate/configure it to route related messages consistently and anticipate partition-count or client-library changes.
Amazon Web Services in Action, Third Edition: An in-depth guide to AWS
A partition key is a DynamoDB primary-key attribute whose value determines an item's partition and can uniquely identify an item when no sort key exists.
- How it is used
- Identifies individual users and groups tasks by user for DynamoDB lookups and queries.
- How deep it goes
- Defines single- and two-attribute keys, then configures tables and demonstrates lookup and query operations; stops short of physical partition internals.
- Examples
- Uses user and task tables, AWS CLI table definitions, and SDK calls that fetch users or list tasks.
- What you can do after
- Apply it via the AWS CLI and DynamoDB SDK to define keys and retrieve items by the access pattern they support.
Microsoft Azure in Action
A partition key is the entity-key component that identifies the physical partition in which an Azure Table Storage entity is stored.
- How it is used
- Identifies an Azure Table Storage entity’s physical partition and guides data placement and access decisions in Cosmos DB.
- How deep it goes
- Defines the Table Storage identifier and works through Cosmos DB selection trade-offs, while deferring deeper Table Storage partition planning.
- Examples
- Uses a PowerShell table-row insertion and an online-store category key to show entity identity and data grouping.
- What you can do after
- Apply it via Add-AzTableRow for Table Storage and evaluate Cosmos DB keys against load distribution and query patterns.
Read how Microsoft Azure in Action explains partitioning key →
Latency
A partitioning key is the data field or value used to determine which partition stores a record.
- How it is used
- Directs complete rows into horizontal partitions and helps identify the partitions affected by a query.
- How deep it goes
- Defines the key through a worked table example and examines distribution failures, but gives no key-selection procedure.
- Examples
- Uses a location-partitioned Users table, unevenly distributed ZIP codes, and differently sized images.
- What you can do after
- Evaluate/understand how a candidate key distributes records and when a key or scheme change may address hot partitions.
100 SQL Server Mistakes and How to Avoid Them
A partitioning key is the column or expression whose values determine the partition containing each table row.
- How it is used
- Uses query-aligned values to divide large tables and reduce reporting reads through partition elimination.
- How deep it goes
- Explains implementation and failure modes, including OR predicates, conversions, and parameterization, but stops short of broader design guidance.
- Examples
- Demonstrates EventTime ranges, ImpressionsArchive read counts, AND-versus-OR predicates, typed variables, and OPTION(RECOMPILE).
- What you can do after
- Diagnose/debug with it by checking whether predicates, data types, and parameterization allow SQL Server to eliminate partitions.
Read how 100 SQL Server Mistakes and How to Avoid Them explains partitioning key →
PostgreSQL Mistakes and How to Avoid Them
A partition key is a column or expression whose values determine how rows are assigned to table partitions.
- How it is used
- Uses keys to route large PostgreSQL tables into partitions suited to timestamp queries and retention maintenance.
- How deep it goes
- Explains range-key DDL, pruning evidence, composite-bound behavior, and sub-partitioning rather than exhaustive partitioning methods.
- Examples
- Demonstrates monthly payments partitions by tstamp and monthly energy-usage partitions further divided by branch_id.
- What you can do after
- Apply it via PostgreSQL DDL to select a range key and model time-first, branch-second partition hierarchies.
Read how PostgreSQL Mistakes and How to Avoid Them explains partitioning key →
Spring in Action, Sixth Edition
A partition key is the component of a Cassandra primary key that determines the partition in which a row is stored.
- How it is used
- Determines which Cassandra partition manages each row during data modeling and persistence mapping.
- How deep it goes
- Explains hash-based placement and demonstrates Spring Data annotations, while deferring detailed partition and cluster mechanics to Cassandra documentation.
- Examples
- Uses a Taco entity whose UUID id is partitioned and whose createdAt value provides descending clustering order.
- What you can do after
- Apply it via Spring Data Cassandra annotations when mapping a domain type to a partitioned table.
Read how Spring in Action, Sixth Edition explains partitioning key →
Akka in Action, Second Edition
A partition key is a value used to deterministically assign an entity or actor to a distribution partition.
- How it is used
- Routes related messages to one routee and identifies sharded actors across cluster nodes.
- How deep it goes
- Explains key extraction, hashing, virtual-node selection, and routee assignment; defers cluster sharding details.
- Examples
- Uses an obfuscator, enricher, and aggregator that share message IDs to join related outputs.
- What you can do after
- Apply it via Akka routers by implementing a stable message-to-key mapping and configuring consistent hashing.
Read how Akka in Action, Second Edition explains partitioning key →
Related concepts
- log compactionuses · Log compaction is a storage technique that retains the latest record for each key while removing superseded records.
- partitionuses · A partition is a distinct subdivision of a larger data, storage, or work unit that can be stored, managed, or processed separately.
- primary keypart of · A primary key is a designated column or attribute, or combination of them, that uniquely identifies each row or item in a table or data store.
- dataset splitconfigures · A dataset split is the division of a dataset into distinct subsets assigned different purposes, such as training, validation, or testing.
These guides are generated from the text of Manning books by Manning's knowledge graph and link to the sections they draw on. The full books are available on liveBook and at manning.com.